Simpson, an Olympic 4x100m relay gold and silver medallist, is a training partner of Powell and took the same substance at the same meet.

Another Jamaican, Olympic discus thrower Allison Randall, was also handed a two-year ban Tuesday for using a prohibited diuretic.

Powell and Simpson, who provided their samples on June 21, 2013, will miss the Commonwealth Games in Glasgow in July.

The three-member disciplinary panel that ruled on Powell said he had been "negligent".

IAAF spokesman Chris Turner said there would be no comment from athletics' world governing body while the case was still open.

Powell, the biggest name in Jamaican sprinting before the rise of double world and Olympic champion Usain Bolt, missed last year's World Championships as a result of his failed test.

In January, he testified that Canadian physical trainer Chris Xuereb provided him with nine supplements, including Epiphany D1.

Xuereb has denied providing performance-enhancing drugs.

Prior to the verdict and in the wake of the Veronica Campbell-Brown case, Powell's coach, Stephen Francis, called on the Jamaican Prime Minister to disband the country's anti-doping organisation and sub-contract the testing procedures to a credible overseas testing agency.

Earlier this year, the Court of Arbitration for Sport cleared Campbell-Brown, a two-time Olympic 200m champion, of a doping violation.

Some facts about drug over which Powell banned

IANS: Oxilofrine, found in the dietary supplement of former world record holder in the 100 m Asafa Powell, is a stimulant drug banned by the World Anti-Doping Agency.

The Jamaican tested positive for the stimulant Oxilofrine at the National Senior Championships last June and has been slapped with an 18-month ban by the Jamaica Anti-Doping Commission.

The substance is an amphetamine found in some dietary supplements and it was developed to treat low blood pressure, reports BBC.

The substance is said to allow people to burn fat faster and lose weight, which is why it is present in some so-called sports nutrition supplements.

But Wayne McLaughlin of Caribbean Toxicology told the Jamaican Anti-Doping Commission during Powell's trial that Oxilofrine "does not improve speed".